Java程序辅导

Socket Programming in 
Java
CS 640 Introduction to Computer Networks
Course Instructor - Ming Liu (mgliu@cs.wisc.edu)
Teaching Assistant - Partho Sarthi (sarthi@wisc.edu)
Office Hours: #3209
WF 1:00PM - 2:00PM
or by appointment
Agenda
1. Introduction
2. What is a Socket? 
3. Methods in Socket API
1.Client Side
2.Server Side
4. Further exploration
CS 640 Introduction to Computer Networks
Introduction
How does one computer send information to another computer?
Request
Response
IP Address – Unique Id on the
network
Port – Unique Id number on your
computer linked to your program
Packet – Data sent from one computer to
another
Client 1
Server
CS 640 Introduction to Computer Networks
Introduction
How does one computer send information to another computer?
Request
Response
IP Address – Unique Id on the
network
Port – Unique Id number on your
computer linked to your program
Packet – Data sent from one computer to
another
IP: 192.168.10.4
Port: 25600
IP: 192.168.10.1
Port: 25500
Client 1
Server
CS 640 Introduction to Computer Networks
Introduction
How does one computer send information to another computer?
IP: 192.168.10.1
Port: 25500
Packet:
How many 
students are 
enrolled in CS 640
IP: 192.168.10.4
Port: 27800
Packet:
Ans:
100
Request
Response
IP Address – Unique Id on the
network
Port – Unique Id number on your
computer linked to your program
Packet – Data sent from one computer to
another
IP: 192.168.10.4
Port: 25600
IP: 192.168.10.1
Port: 25500
Client 1
Server
CS 640 Introduction to Computer Networks
What is a Socket?
• Sockets allow communication between two different 
processes on the same or different machines.
• A socket is bound to a port number so that the transport layer 
can identify the application that data is destined to be sent to.
CS 640 Introduction to Computer Networks
What is a Socket?
Server Socket 
Object
Waiting
Server
CS 640 Introduction to Computer Networks
What is a Socket?
Socket Object
Server Socket 
Object
Waiting
Client 1
Server
CS 640 Introduction to Computer Networks
What is a Socket?
Socket Object
Socket Object
Waiting
Client 1
Server Socket 
Object
Server
CS 640 Introduction to Computer Networks
What is a Socket?
Socket Object
Socket Object
Waiting
Client 1
Server Socket 
Object
Server
CS 640 Introduction to Computer Networks
What is a Socket?
Socket Object
Socket Object
Socket Object
Waiting
Client 1
Client 2
Server Socket 
Object
Server
CS 640 Introduction to Computer Networks
What is a Socket?
Socket Object
Socket Object
Socket Object
Socket Object
Waiting
Client 1
Client 2
Server Socket 
Object
Server
CS 640 Introduction to Computer Networks
Methods in Socket API
Client Side –
1.Create a Socket object:
Socket socket = new Socket(address, port); 
2. Create an Output Writer:
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
3. Write the message:
out.println(msg);
4. Close the connection:
out.close();
socket.close();
CS 640 Introduction to Computer Networks
Methods in Socket API
Server Side –
1.Create a Server Socket object:
ServerSocket server = new ServerSocket(port);
2. Wait for Client and then create a Socket object:
Socket socket = server.accept();
3. Create an Input Reader:
in = new BufferedReader(InputStreamReader(socket.getInputStream()));
3. Read and Display the message:
line = in.readLine();
4. Close the connection:
in.close();
socket.close();
server.close(); CS 640 Introduction to Computer Networks
Watch the Walkthrough Video
CS 640 Introduction to Computer Networks
Further exploration
• Keep the server running till a “quit” message is received.
• Multiple clients – synchronous and asynchronous communication.
(Hint – see Threads in Java)
Reading :
• Lesson: All About Sockets (The Java™ Tutorials) (oracle.com)
• Socket Programming in Java
CS 640 Introduction to Computer Networks
Thank You
CS 640 Introduction to Computer Networks
Use Piazza for any doubts